1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161

use cairo_lang_defs::ids::MemberId;
use cairo_lang_proc_macros::DebugWithDb;
use cairo_lang_semantic as semantic;
use cairo_lang_semantic::expr::fmt::ExprFormatter;
use cairo_lang_utils::extract_matches;
use cairo_lang_utils::ordered_hash_map::OrderedHashMap;

use super::usage::MemberPath;
use crate::db::LoweringGroup;
use crate::VariableId;

/// Maps member paths ([MemberPath]) to lowered variable ids.
#[derive(Clone, Default, Debug)]
pub struct SemanticLoweringMapping {
    scattered: OrderedHashMap<MemberPath, Value>,
}
impl SemanticLoweringMapping {
    /// Returns the topmost mapped member path containing the given member path, or None no such
    /// member path exists in the mapping.
    pub fn topmost_mapped_containing_member_path(
        &mut self,
        mut member_path: MemberPath,
    ) -> Option<MemberPath> {
        let mut res = None;
        loop {
            if self.scattered.contains_key(&member_path) {
                res = Some(member_path.clone());
            }
            let MemberPath::Member { parent, .. } = member_path else {
                return res;
            };
            member_path = *parent;
        }
    }

    /// Returns the scattered members of the given member path, or None if the member path is not
    /// scattered.
    pub fn get_scattered_members(&mut self, member_path: &MemberPath) -> Option<Vec<MemberPath>> {
        let Some(Value::Scattered(scattered)) = self.scattered.get(member_path) else {
            return None;
        };
        Some(
            scattered
                .members
                .iter()
                .map(|(member_id, _)| MemberPath::Member {
                    parent: member_path.clone().into(),
                    member_id: *member_id,
                    concrete_struct_id: scattered.concrete_struct_id,
                })
                .collect(),
        )
    }

    pub fn get<TContext: StructRecomposer>(
        &mut self,
        mut ctx: TContext,
        path: &MemberPath,
    ) -> Option<VariableId> {
        let value = self.break_into_value(&mut ctx, path)?;
        Self::assemble_value(&mut ctx, value)
    }

    pub fn introduce(&mut self, path: MemberPath, var: VariableId) {
        self.scattered.insert(path, Value::Var(var));
    }

    pub fn update<TContext: StructRecomposer>(
        &mut self,
        mut ctx: TContext,
        path: &MemberPath,
        var: VariableId,
    ) -> Option<()> {
        let value = self.break_into_value(&mut ctx, path)?;
        *value = Value::Var(var);
        Some(())
    }

    fn assemble_value<TContext: StructRecomposer>(
        ctx: &mut TContext,
        value: &mut Value,
    ) -> Option<VariableId> {
        Some(match value {
            Value::Var(var) => *var,
            Value::Scattered(scattered) => {
                let members = scattered
                    .members
                    .iter_mut()
                    .map(|(_, value)| Self::assemble_value(ctx, value))
                    .collect::<Option<_>>()?;
                let var = ctx.reconstruct(scattered.concrete_struct_id, members);
                *value = Value::Var(var);
                var
            }
        })
    }

    fn break_into_value<TContext: StructRecomposer>(
        &mut self,
        ctx: &mut TContext,
        path: &MemberPath,
    ) -> Option<&mut Value> {
        if self.scattered.contains_key(path) {
            return self.scattered.get_mut(path);
        }

        let MemberPath::Member { parent, member_id, concrete_struct_id, .. } = path else {
            return None;
        };

        let parent_value = self.break_into_value(ctx, parent)?;
        match parent_value {
            Value::Var(var) => {
                let members = ctx.deconstruct(*concrete_struct_id, *var);
                let members = OrderedHashMap::from_iter(
                    members.into_iter().map(|(member_id, var)| (member_id, Value::Var(var))),
                );
                let scattered = Scattered { concrete_struct_id: *concrete_struct_id, members };
                *parent_value = Value::Scattered(Box::new(scattered));

                extract_matches!(parent_value, Value::Scattered).members.get_mut(member_id)
            }
            Value::Scattered(scattered) => scattered.members.get_mut(member_id),
        }
    }
}

/// A trait for deconstructing and constructing structs.
pub trait StructRecomposer {
    fn deconstruct(
        &mut self,
        concrete_struct_id: semantic::ConcreteStructId,
        value: VariableId,
    ) -> OrderedHashMap<MemberId, VariableId>;
    fn reconstruct(
        &mut self,
        concrete_struct_id: semantic::ConcreteStructId,
        members: Vec<VariableId>,
    ) -> VariableId;
    fn var_ty(&self, var: VariableId) -> semantic::TypeId;
    fn db(&self) -> &dyn LoweringGroup;
}

/// An intermediate value for a member path.
#[derive(Clone, Debug, DebugWithDb)]
#[debug_db(ExprFormatter<'a>)]
enum Value {
    /// The value of member path is stored in a lowered variable.
    Var(VariableId),
    /// The value of the member path is not stored. It should be reconstructed from the member
    /// values.
    Scattered(Box<Scattered>),
}

/// A value for an non-stored member path. Recursively holds the [Value] for the members.
#[derive(Clone, Debug, DebugWithDb)]
#[debug_db(ExprFormatter<'a>)]
struct Scattered {
    concrete_struct_id: semantic::ConcreteStructId,
    members: OrderedHashMap<MemberId, Value>,
}